This invention generally relates to in-situ perfusion of an organ in a human or animal. In particular, the invention relates to a perfusion catheter for providing supplemental blood flow to a kidney.
A long-felt need exists for a renal therapy device that perfuses kidney(s) with blood or another perfusion substance for extended periods, such as for days. Kidneys filter blood to remove body fluids, sodium and toxins, which are expelled from the body as urine. The filtration of blood is performed by a specialized network of capillaries in the kidneys. To properly pass through the kidneys, the blood pressure at the renal artery (the inlet to the kidneys) should be sufficient to force the blood through the network of capillaries.
Kidneys function best when the blood pressure is within a range of normal mean blood pressures, e.g., 60 to 120 mm Hg. When the blood pressure in the renal artery falls below this range of normal pressure, blood does not pass through the kidneys in sufficient volume to properly filter all of the blood in a circulatory system of a patient. Under low blood pressure conditions, the kidneys suffer from impaired renal perfusion which results in a decrease in urine output (and hence a corresponding build-up of fluids, sodium and toxins in the body), unfavorable change of neurohormonal stimulation and increased vasoconstriction (contraction of blood vessels). Prolonged impaired renal perfusion can lead to acute tubular necrosis, renal failure and ultimately dependency on artificial kidney for life.
Impaired renal perfusion may result from chronic heart failure. Chronic heart failure is a condition in which the heart typically deteriorates over an extended period of time, e.g., months or years. Heart failure is a clinical syndrome or condition characterized by (1) signs and symptoms of intravascular and interstitial volume overload, including shortness of breath, fluid in lungs, and edema, and (2) manifestations of inadequate tissue perfusion, such as fatigue or poor exercise tolerance. These signs and symptoms result when the heart is unable to generate a cardiac output sufficient to meet the body""s demands. Heart failure is a major public health problem. The National Heart, Lung, and Blood Institute has estimated that more than 5 million Americans have heart failure and that about 400,000 new cases of heart failure are diagnosed each year. Total treatment costs for heart failure-including physician visits, drugs, and nursing home staysxe2x80x94were more than $10 billion in 1990.
A failing heart may not be able to generate sufficient blood pressure to properly perfuse the kidneys. A healthy heart pumps blood by increasing the kinetic energy (pressure and/or velocity) of the blood flowing through a person""s circulatory system. The energy imparted by a heart to the blood flow is normally sufficient to cause the blood to circulate through the lungs, kidney and other organs of a human body. A failing heart is generally unable to maintain normal blood pressure within the circulatory system of a person. Blood pressure tends to progressively decrease as the heart. progressively fails in a patient suffering from chronic heart failure. Accordingly, chronic heart failure can lead to chronic impaired renal perfusion. Chronic heart failure patients are frequently admitted to the hospital with an onset of acute heart failure, which is an abrupt worsening of their condition that requires intensive care. During these periods of acute hypotension (or low blood pressure) their kidneys are particularly at risk from hypotension and can be severely injured.
There is a long-felt (although unrecognized) need for devices that can treat chronic impaired renal perfusion and, specifically, treat this condition in connection with the acute and chronic heart failure. In this condition patients blood pressure falls below the minimum level required for kidney function. As a result patients are admitted to the hospital with fluid overload resulting from the retention of fluid and sodium by the kidneys. To treat fluid overload, a device is needed that increases the arterial blood pressure at the kidney for extended periods, such as for several days.
In clinical practice it is sometimes desirable to isolate and perfuse an organ, such as the kidney, brain or liver. An organ suffering from inadequate blood flow, e.g., low systemic arterial pressure, may result in ischemia, organ shutdown or stroke. Extracorporeal perfusion of an organ is the process of artificially providing supplemental blood to that organ from an external source, usually a blood pump. The supplemental blood flow to the organ enables the organ to continue function properly, to avoid distressing the organ and may protect or revive an organ suffering from inadequate blood flow.
During perfusion, the blood or blood substitute is supplied to the organ by extracorporeal circuits from an external source, or may be blood drawn from the body and pumped by back into the body at the organ. An extracorporeal circuit, such as a blood pump connected by tubes and catheters to the body, may provide the blood to the organ for perfusion. The blood pump increases the kinetic energy of the blood or the perfusate, increases the perfusion pressure gradient, and sometimes, an oxygenator to add oxygen to the blood stream.
A kidney perfusion catheter is a device that increases the blood pressure at the kidney, and specifically in the renal artery. A catheter is typically a long, thin tube inserted through a patient""s skin and into an artery or a vein. The catheter is connected at one end (commonly referred to as its proximate end) to a blood or saline bag, a blood pump or other medical device external to the body. Many people have had short catheters inserted into a vein in their arm to draw blood for blood donations, dialysis, or to receive blood during hospitalization.
Longer catheters exist that are inserted through the skin at the groin into the femoral artery (or vein). These longer catheters are advanced by an interventional radiologist or cardiologist through the artery to a body organ, such as the heart or kidney. These longer catheters often include guide wires, lumens, balloons, and other devices that perform a variety of catheter functions within an artery or organ. For example, a guide wire typically assists the physician in maneuvering the tip of the catheter along the passages of an artery to the intended position in the artery or organ. Once the catheter is properly positioned within a blood vessel, an instrument can be advanced via an internal lumen of the catheter to perform a therapeutic clinical intervention such as an ablation or dilatation or a diagnostic intervention such as angiography. Lumens are typically tubular passages within the catheter for the guide wires, sensor wires, and to pass blood or other fluids through the catheter.
Catheters exist for short-term perfusion of organs during cardiac surgery and other operations. Surgeons also are known to temporarily perfuse selected organs with extracorporeal pumps when major blood vessels, such as the aorta, are being repaired during surgery, vascular intervention and medical treatment. In addition, kidney perfusion catheters have been disclosed that perfuse kidneys in a dead patient until the kidneys are harvested for transplant. These catheters are not suitable for use beyond a few minutes or hours, and would be injurious to the patient if used for several days.
Existing catheters for in-situ perfusion of isolated organs or parts of the body with blood or chemical include a catheter for pelvic perfusion that isolates a portion of a major artery with two occluding balloons. The balloons are attached to a catheter to form a dumb-bell shape in which the balloons are at opposite ends of a tubular catheter section. The balloons anchor the catheter in an artery, form dams blocking the artery and allow the catheter to increase the blood pressure in the arterial section between the balloons. Fluid is infused by the catheter into the space between two balloons to perfuse organs that are connected to arterial branches stemming the isolated segment of the artery between the balloons.
The dumb-bell balloon catheters are not suited to long-term perfusion of kidneys. If an aortic balloon catheter is not properly positioned, it may accidentally occlude the renal artery, mesenteric artery and other blood passages near the branch for the renal artery. These arteries may also become occluded as a result of the shifting of the catheter if the patient moves or is moved or rolled as it is common in medical practice. Presence of an occluding balloon in the aorta downstream of the left ventricle will increase the resistance to the ejection of the blood by the left ventricle (main pumping chamber) of the heart and is highly undesirable in patients suffering from heart failure. By increasing the downstream resistance to blood flow, an occluding balloon increases the workload on the failing heart and, thus, directly undermines the treatment of the heart which usually includes decreasing vascular resistance that the heart must overcome.
Another existing catheter has a perfusion cannula tipped with an occluding inflatable balloon are commonly used to perfuse organs in-situ, and include coronary sinus retrograde perfusion catheters for supplying blood or cardioplegia solution to the heart during cardiac surgery. The balloon on the tip of the catheter is inflated with gas or liquid until the balloon is expanded to form a tight seal between the balloon and the walls of the blood vessel or the body cavity. Perfusate, e.g., blood, saline or other oxygen carrying fluid, is pumped into the main lumen of the catheter at a flow rate needed to achieve the desired organ perfusion pressure. A similar device (Pruitt-Inhara shunt) has been used to protect kidneys from hypotension during aortic surgery.
In current balloon tipped perfusion catheters, the balloon is introduced into a blood vessel and inflated to a relatively-high pressure (significantly higher than the normal blood pressure) until the balloon fits tightly against the blood vessel wall, dilates the wall and totally occludes the vessel passages. The perfusate flow is initiated creating an elevated pressure zone distal of the balloon that is substantially higher than the pressure in the artery proximal to the balloon.
Balloon-tipped catheters can xe2x80x9cdriftxe2x80x9d or migrate proximally (out of the vessel) owing to the distal-to-proximal pressure gradient. The balloon is generally prevented from moving by the friction between the external surface of the balloon and the vessel wall. Ribs, dimples, barbs and other similar features are put on the outer surface of the balloons to increase the friction force and prevent drifting of the balloon in the blood vessel.
If a balloon-tipped perfusion catheter remained inflated in a blood vessel for several days, certain adverse effects would result. The continuous pressure applied by the balloon can damage or completely destroy the endothelium (innermost layer of the blood vessel). Although relatively small areas (less than 3 cm) of the blood vessel stripped off the endothelium are likely to recover over time, blood clots might form in the vessel as the result of the injury and cause acute thromboses. The continuous distention of the wall of an artery by an inflated balloon may prevent oxygen from reaching the walls in contact with the balloon and can result in the transmural ischemia of the wall tissue and tissue necrosis. This condition can lead to the development of an aneurysm, rupture and severe internal injury and bleeding.
If a totally-occluding partition of a catheter is introduced distally to the entrance into an artery, blood flow will completely cease in the branch of the artery proximal to the occlusion. Properties of blood are such that a clot is likely to form in the stagnant pools of blood with no circulation. This is especially likely if the blood is in contact with any material other than the natural internal lining of the vessel. Later, when the catheter is removed, the clot may drift downstream in the perfused or an adjacent artery and can cause a total occlusion of a vital artery and shut-down of blood flow to a vital organ.
In existing perfusion catheters, the catheter is held in place by the same means that partition and seal the perfused organ artery (in most cases an inflatable balloon). In an organ such as a kidney that relies on one major artery for a substantial part of its oxygenated blood perfusion such catheter that seals the renal artery for extended periods of time by distending its walls could damage the artery and kidney. A catheter is needed that seals and unseals the passage of the kidney artery to permit blood to flow naturally to the kidney (when the catheter is unsealed) and, alternatively, to provide perfusion or perfusion from an external blood pump as needed.
A kidney perfusion catheter is needed that may be used during the extended treatment, e.g., several days, of acute hypotension (low blood pressure) resulting from heart failure or to prevent an impeding renal failure in an intensive care unit of a hospital. The catheter is inserted into the patient, for the duration of hypotension that is potentially injurious to the kidney can last as long as two or three days. It was also desired to have a catheter that does not require extensive surgery to be inserted into a patient to the perfused artery to a kidney. The catheter would preferably be introduced and secured using common minimally invasive percutaneous technique by an interventional cardiologist or radiologist in a catheterization laboratory.
A novel kidney perfusion catheter assembly has been developed having an introducer catheter shaft, a reversible sealing mechanism, a perfusion tip, and a guide wire. The perfusion catheter assembly provides a flow of supplemental blood to increase the local blood pressure in the renal artery and to perfuse the kidney. The perfusion catheter includes an introducer catheter, a perfusion catheter tip and a guide wire. The perfusion catheter assembly is inserted into the femoral artery through an incision in the skin at the groin of a patient. The introducer catheter is maneuvered through the femoral artery into the abdominal aorta and positioned opposite the ostium (entrance) into the renal artery.
The perfusion catheter tip is telescoped from the distal end of the introducer catheter into the renal artery. The introducer catheter has a small diameter that does not substantially obstruct blood naturally flowing through the aorta. The catheter tip has a small diameter that does not substantially obstruct blood naturally flowing from the aorta into the renal artery until the seal mechanism is activated. A blood pump attached to the proximal end of the perfusion catheter assembly provides a flow of blood that streams from the perfusion catheter tip into the renal artery. This stream of blood increases the pressure and volume of the blood flowing through the renal artery and into the kidney.
The perfusion catheter assembly is suitable for long term, e.g., several days or longer, treatment of impaired renal perfusion. The catheter assembly has several distinctive characteristics, including (without limitation and without requirement that all distinctive characteristics be included in each embodiment of the catheter assembly):
a) The catheter assembly is introduced percutaneously via a femoral artery and the bulk of the catheter assembly remains in the femoral artery and the lower aorta. To avoid excessive obstruction of blood flow to lower body and resulting ischemia, the introducer catheter, preferably has an external diameter of 9 or 8 French or less.
b) The catheter assembly is capable of delivering approximately 500 ml/min of blood to the renal artery in conjunction with a peristaltic roller blood pump or a centrifugal blood pump. The blood is pumped from an extracorporeal blood pump, through an inner lumen of an introducer catheter, into a smaller perfusion catheter tip, and is discharged from the perfusion catheter tip into the renal artery. The volume blood flow requires an internal lumen diameter of the introducer catheter sufficient to avoid the need for high pressure and high velocity blood flow that would require the use of high-pressure pump technologies and could damage the blood due to high shear stress resulting from excessive blood velocity.
c) The perfusion catheter tip, which is the portion of the catheter penetrating the renal artery, preferably is of a small outer diameter, such as 6 French or less.
d) A sealing device, e.g., balloon, on the introducer catheter distal edge substantially seals the entrance into renal artery, e.g., at the ostium, to ensure that the perfusion sufficiently increases the blood pressure seen by the kidney without substantially distending the walls of the renal artery. The sealing device also allows for continued blood flow through the aorta to the lower portions of the body (including the legs) and may allow for circulatory flow into the renal artery, around the catheter tip, and into the kidney when inactivated without the removal of the catheter. An additional partitioning device may be added to the catheter tip to dam or partition the renal artery, create additional resistance to the runoff of the perfusion fluid without substantial ally contacting or distending the walls of the renal artery.
e) The catheter tip remains anchored in the renal artery for several days, and should not drift from its position in that artery, even as the patient is moved. Anchoring is achieved by: (a) attachment of the proximal end of the catheter to the skin at the groin; (b) substantial penetration of the catheter tip into the renal artery; (c) bracing of the introducer catheter across the aorta against the aortic wall opposite to the perfused renal artery entrance.
In operation, the kidney perfusion catheter apparatus is introduced into the femoral artery percutaneously, advanced into the aorta and further into the renal artery (tip only) using common methods under fluoroscopic guidance. The catheter includes at least one perfusion lumen for the infusion of blood under pressure. The catheter remains in the renal artery for several days to deliver perfusate to at least one kidney, to protect the kidney(s) from hypotension and normalize renal function. The catheter may have components that secure and immobilize the catheter with the perfusion tip in the renal artery, safely seal and/or partition the renal artery to substantially prevent retrograde flow from that artery into the aorta, and to monitor renal artery pressure in the perfused zone.
Inserting a renal artery perfusion catheter into the human aorta and into renal arteries is difficult. The renal arteries are approximately 4 to 6 mm in diameter in an adult. The aorta is 20 to 25 mm in diameter. The renal arteries branch from the aorta at an angle of 90 to 60 degrees slanted down towards the patient""s legs. When inserted into the femoral artery at the groin, the catheter must turn sharply to enter the renal artery. In a renal artery with arteriosclerosis the plaque tends to concentrate in the area of the ostium or entry from the aorta into the renal artery. If the plaque is disturbed and separated from the vessel wall it may float into the kidney and cause severe complications.
A guide wire and guiding catheter have been used to insert catheters that engage and cross into the renal artery for diagnostic catheterization and angioplasty. A guiding catheter is generally a preshaped plastic tube that can be straightened when it is introduced into the femoral artery via a straight sheath catheter. The internal lumen of the catheter houses the guide wire that forces the catheter to remain straight as the catheter and the guide wire are moved through the femoral artery and into the aorta. Once the distal tip of the sheath catheter has been positioned in the aorta and in the vicinity of the renal artery, the guide wire moves axially out of the catheter. The catheter has substantial material memory to resume (recoil) into its curve when it is in the aorta and has enough space to make a turn. A relatively-stiff guide wire can assist in straightening and recoiling of the catheter as needed to traverse the vascular passage. The preshaped curve, e.g., a J-hook or a Cobra hook that spans the diameter of the aorta, of the introducer catheter makes possible the turn that the perfusion catheter has to make to engage the renal artery ostium in the wall of the aorta and to provide a bias (due to the resilience of the hook) that forces the perfusion catheter against the ostium of the renal artery.
In addition, the perfusion catheter would preferably be placed in the renal artery at a catheterization laboratory, but the perfusion does not start until the patient is moved to the intensive care unit (ICU) area of the hospital. Moving a patient with an external perfusion system attached and pumping blood is possible, but presents a logistical challenge. The present perfusion catheter assembly allows for a procedure of inserting the catheter into the renal artery, moving the patient to an ICU, and starting perfusion of the kidney using the catheter after the patient has been safely placed in the ICU.